Adhesive composition and tapes and labels dervived therefrom

ABSTRACT

Adhesive composition for tapes, labels and bandages to be used at temperatures of +5° C. and lower, comprising (a) at least one block copolymer, comprising at least two terminal blocks of poly(vinyl aromatic compound) and at least one midblock of a randomly copolymerized mixture of isoprene and butadiene, optionally mixed with a diblock copolymer comprising one poly(vinyl aromatic compound) block and one randomly copolymerized mixture of isoprene and butadiene, and optionally mixed with a block copolymer, comprising at least one block of poly(vinyl aromatic compound) and at least one block of poly(butadiene) or poly(isoprene), (b) at least one mixed aliphaticlaromatic tackifying resin or a blend of aliphatic and aromatic tackifying resins, having an aromatic H-NIVIR content between 6 and 22%, and (c) a plasticizer in an amount of at most 25 wt %, relative to the weight of the adhesive composition; and tapes, labels and bandages comprising said adhesive compositions, applied on a substrate layer; and the use of said tapes, labels or bandages.

BACKGROUND ART

Adhesive compositions based on styrenic block copolymers asthermoplastic elastomer components are well known in the art. Thesecompositions are for instance used in pressure sensitive adhesive (PSA)for industrial tapes, packaging tapes, labels and bandages (e.g.plasters).

More in particular styrene-isoprene-styrene block copolymers (S-I-S) andstyrene-butadiene-styrene block copolymers (S-B-S) are widely used inthese adhesive compositions. Both classes of block copolymers give theadhesive compositions specific properties related to the respectiveinherent characteristics of these block copolymers.

For example, the softness of S-I-S makes this polymer type the materialof choice for pressure sensitive applications in tapes and labels, whilethe elevated cohesion of S-B-S makes this material attractive forconstruction adhesives for disposable soft goods.

S-I-S block copolymers have until now successfully been applied inindustrial and packaging tape and label applications.

More in particular, from e.g. U.S. Pat. No. 5,389,438 (MINNESOTA MININGMFG) 02.12.1995; EP 306232 A (MINNESOTA MINING MFG) 08.03.1989; EP443263 A (MINNESOTA MINING MFG) 28.08.1991; WO 0014170 (EXXON) 16.032000and U.S. Pat. No. 6,384,138 (EXXON) 07.05.2002 adhesive compositions tobe used for tapes, labels, bandages or disposable sanitary articles,such as diapers and incontinence garments, were known. Said adhesivecompositions comprised:

-   1. at least one block copolymer, comprising at least two terminal    blocks of poly(vinyl aromatic compound) and at least one midblock of    poly(isoprene) or poly(butadiene) or poly(ethylene-butylene), i.e.    hydrogenated poly(butadiene, or a mixture of said block copolymers,-   2. at least one tackifying resin, and-   3. a plasticizer.

It will be appreciated that in none of said publications any referenceis made to the use of the adhesive compositions at low temperatures,i.e. below room temperature.

Although in particular S-I-S block copolymer containing compositionsshowed outstanding tack, peel and cohesion at room temperature, i.e. attemperatures around 20° C., they have appeared to lack adequate adhesiveproperties in cold environments, namely 5° C. and below.

It is well known from e.g. Handbook of Pressure Sensitive AdhesiveTechnology, Don Satas, Chapter 13, Thermoplastic Rubbers, A-B-A blockcopolymers, p 367 (1989, 2^(nd) ed.), that most adhesive compositionsbased on S-I-S block copolymers loose their tack and adhesion propertiesas temperature decreases from about 15° C.

It was possible to formulate adhesive compositions based on S-I-S blockcopolymers, having a good tack below 15° C., but in order to achieve anacceptable compromise with the adhesive properties, relatively lowproportions of high softening point hydrocarbon resins and relativelyhigh proportions of plasticizers are needed.

However, high proportions of plasticizer have the disadvantages (a) thatthe peel and cohesion of the adhesive is reduced and (b) that theplasticizer migrates out of the formulation, modifying the visual andproperty appearance of the final products, like oily spots in a paperlabel.

During the splitting of roll products, too much oil generates edgeoozing, provoking that two adjacent rolls stick together.

Therefore there is a strong need for adhesive compositions which keepgood tack, adhesion and cohesion at low temperatures, and more inparticular at temperatures in the range from +5 to −25° C., whichenables the manufacture of tapes and labels to be used in coldenvironments e.g. some electrical insulating tapes or on frozenarticles, e.g. food and medicines in deep freezers.

It is an object of the present invention to provide adhesivecompositions which keep good tack, adhesion and cohesion at lowtemperatures, and which do not contain high amounts of plasticizers.

Another object of the present invention is formed by labels and tapeswhich retain adequate properties when stored for a long time at lowtemperatures.

Another object of the present invention is to provide adhesivecompositions which enable the manufacture of repositionable or removabletapes, labels and bandages (e.g. plasters) which can be used at lowtemperatures.

As result of extensive research and experimentation, said adhesivecompositions aimed at, and labels, tapes and bandages to be manufacturedfrom them, have now surprisingly been found.

DISCLOSURE OF THE INVENTION

Accordingly the present invention relates to an adhesive composition fortapes, labels and bandages to be used at temperatures of +5° C. andlower, comprising

(a) at least one block copolymer, comprising at least two terminalblocks of poly(vinyl aromatic compound) and at least one midblock of arandomly copolymerized mixture of isoprene and butadiene, said blockcopolymer being optionally mixed with a diblock copolymer, comprisingone poly(vinylaromatic) block and one randomly copolymerized mixture ofisoprene and butadiene, and optionally mixed with a block copolymer,comprising at least one block of poly(vinyl aromatic compound) and atleast one block of poly(butadiene) or poly(isoprene),

(b) at least one mixed aliphatic/aromatic tackifying resin or a blend ofaliphatic and aromatic tackifying resins, having an aromatic H-NMRcontent between 6 and 22%, and

(c) a plasticizer in an amount of at most 25 wt %, relative to theweight of the adhesive composition,

and to tapes, labels and bandages derived from it.

MODE(S) FOR CARRYING OUT THE INVENTION

Component (a)

The main block copolymer component used in the adhesive composition is ablock copolymer, having a structure represented by the general formulaeS-(I/B)-S (1) or [S-(I/B)]_(n)X (2), optionally mixed with a diblockcopolymer S-(I/B), and optionally mixed with minor amounts of one ormore block copolymers, selected from the group S-B, S-B-S, S-I andS-I-S, wherein S represents a poly(vinyl aromatic compound) block, (I/B)represents a block of a randomly copolymerized mixture of isoprene andbutadiene, wherein the weight ratio between isoprene and butadiene is inthe range of from 70:30 to 30:70, or in a mole/mole ratio of from1.1/0.55 to 0.45/1.3, wherein B represents a poly(butadiene) blockwherein I represents a poly(isoprene) block, wherein n is an integerequal to or greater than 2, and wherein X is the residue of a couplingagent.

Preferred weight ratios between isoprene and butadiene are in the rangeof from 60:40 to 30:70 or in a molar ratio of from 0.89/0.75 to0.45/1.3.

As an example of the aromatic vinyl compound useful in the practice ofthe present invention, may be mentioned styrene, alpha-methylstyrene,p-methylstyrene, o-methylstyrene, p-tert.butylstyrene, dimethylstyrene,and vinyl naphthalene or mixtures thereof. Of these, styrene isparticularly preferred from the viewpoints of easy availability,reactivity, physical properties of the resulting block copolymers. The Apolymer block may contain minor amounts of comonomers other than anaromatic vinyl compound, e.g., up to 5 wt % of a copolymerizable monomersuch as butadiene and/or isoprene (based on the weight of the totalblock). Most preferred are A blocks derived from substantially purestyrene.

These polymer blocks A preferably have a true molecular weight in therange from 9,500 to 25,000.

The mixed polymer midblock (I/B) is made of butadiene and isoprene ascopolymerizing monomers, although it too may contain minor amounts ofother comonomers, e.g. up to 5 wt % of a copolymerizable monomer such asstyrene (based on the weight of the total block), but mixtures ofsubstantially pure isoprene and butadiene are preferred.

In the block copolymers according to the present invention, theproportion of bound aromatic vinyl compound is in the range of 10-50 wt%, preferably 15 wt % based on the total block copolymer. The proportionof bound butadiene is 18-80 wt %, preferably 40-70 wt % in total. Theproportion of bound isoprene is 15-70 wt %, preferably 30-70 wt %. Theseamounts of bound monomers (plus copolymerizable monomers, if any) add upto 100 wt %.

The block copolymers to be applied in the adhesive compositionsaccording to the present invention each preferably have a weight averagemolecular weight (Mw, expressed in terms of polystyrene) ranging from100,000 to 500,000, preferably from 150,000 to 250,000 as determined bygel permeation chromatography (GPC, analogous to the method described inASTM D5296-97).

The block copolymers to be applied in the adhesive compositionsaccording to the present invention each preferably contain 1,2-vinylbonds and/or 3,4-vinyl bonds in a proportion in the range of from 5 to40 wt % based on the weight of the conjugated diene or in the range offrom 0.08 to 0.70 mole/mole %, and preferably from 5 to 20 wt %, basedon the weight of conjugated diene or 0.08 to 0.35 mole/mole %. The blockcopolymers according to the present invention preferably each have astorage modulus (G′) of 1 to 300 MPa in a visco-elasticity measurementin a temperature range of from 0 to 50° C., and only one peak on losstangent (tan δ) attributable to the mixed butadiene/isoprene polymerblock at a temperature of −50° C. or below. When a block copolymerhaving a storage modulus (G′) lower than 1 MPa is used as a base polymerfor a pressure sensitive adhesive, then the holding power of the PSA islowered. On the other hand, any storage modulus exceeding 300 MParesults in a pressure sensitive adhesive lowered in tackiness.

Said block copolymers to be applied as main component (a) in theadhesive composition, have a randomly copolymerized block (I/B), whichmeans that the mixed midblock shows no significant single homopolymerblock formation.

They can be prepared as described in WO 02057386 (KRATON) 25.07.2002,which is herein incorporated by reference.

More in particular, polymers having mixed midblocks may be defined ashaving average homopolymer block lengths of less than 100 monomer units,preferably less than 50 monomer units, more preferably less than 20monomer units.

Average homopolymer block length may be determined by carbon-13 NMR, asdescribed in detail in WO 02057386.

The block copolymers according to the present invention can be made e.g.by coupling living diblock copolymer prepared by anionic polymerizationwith a coupling agent.

As examples of the coupling agent may be mentioned tin coupling agentssuch as tin dichloride, monomethylin dichloride, dimethyitin dichloride,monoethyltin dichloride, diethyltin dichloride, methyltin trichloride,monobutyltin dichloride, dibutyltin dibromide, monohexyltin dichlorideand tin tetrachloride; halogenated silicon coupling agents such asdichlorosilane, monomethyldichlorosilane, dimethyldichlorosilane,monoethyldichlorosilane, diethyldichlorosilane, monobutyldichlorosilane,dibutyldichlorosilane, monohexyldichlorosilane, dihexyldichlorosilane,dibromosilane, monomethyldibromosilane, dimethyldibromosilane, silicontetrachloride and silicon tetrabromide; alkoxysilanes such astetramethoxysilane; divinyl aromatic compounds such as divinylbenzeneand divinylnaphthalene; halogenated alkanes such as dichloroethane,dibromoethane, methylene chloride, dibromomethane, dichloropropane,dibromopropane, chloroform, trichloroethane, trichloropropane andtribromopropane; halogenated aromatic compounds such as dibromobenzene;epoxy compounds such as the diglycidyl ether of bisphenol-A and the like(e.g., EPON™ 825 or EPON™ 826 diglycidyl ether) and other couplingagents such as benzoic esters, CO, 2 and 1-chloro-1,3-butadiene. Ofthese, EPON™ 826 diglycidyl ether, dibromobenzene, tetramethoxysilane orother tetra(alkoxy)silanes are preferred.

The main block copolymer in component (a) may hence comprise a mixtureof the coupled polymer according to the general formulae (1) or (2) andof the intermediate diblock, e.g. in a weight ratio of 100/0 to 30/70.

It will be appreciated that the main block copolymer component (a) mayalso be formed by a block copolymer obtained by sequentialpolymerization of batches of the respective monomers (e.g. styrene andmixtures of butadiene/isoprene, optionally in combination withreinitiation, if additional diblock copolymer is desired.

The block copolymers of formulae (1) and (2) can be made by mereadaptation of common processes used for the preparation of S-B-S typeblock copolymers and/or S-I-S type block copolymers, using a mixture ofbutadiene/isoprene instead. Of importance in the preparation of theblock copolymers according to the present invention is to avoidhomopolymer block formation, to ensure appropriate B/I ratio, and toproduce a polymer block wherein the random midblock has a Tg of −50° C.or less. Generally no randomizer will be used.

As specified hereinbefore, the main block copolymer of formulae (1) or(2), which usually will comprise corresponding diblocks, can be mixedwith minor proportions of conventional diblock copolymers and/ortriblock copolymers, comprising poly(vinyl aromatic compound) blocks andpoly(butadiene) blocks or poly(isoprene) blocks in a proportion of from0 to 50 wt %, relative to the weight of component (a) and preferably ina proportion of from 0 to 30 wt %.

More preferably said diblock copolymers and triblock copolymers havebeen obtained in one process, comprising the preparation of an initialliving diblock, which can be subsequently coupled to a triblockcopolymer by means of a coupling agent as specified hereinbefore.

It will be appreciated that the diblock copolymer and/or triblockcopolymers, which can optionally be incorporated in component (a), mayhave apparent molecular weights which are about the half of those of themain block copolymer component for an additional copolymer diblock andabout the same as those of the main block copolymer for an additionaltriblock copolymer respectively.

Component (b)

Suitable tackifying resins or mixtures of resins have been found to havean aromatic H-NMR content between 6 and 22%, and preferably from 9 to22%, and more preferably from 9 to 18%. More preferred tackifying resinsshow a differential scanning calorimetry (DSC) glass transitiontemperature Tg between 30° C. and 40° C., and preferably between 35 and38° C., and a Ring and Ball softening point between 80° C. and 90° C.

They can be selected from modified aliphatic hydrocarbon resins such asmodified C5 hydrocarbon resins (C5/C9 resins), styrenated terpeneresins, partially hydrogenated C9 hydrocarbon resins and mixturesthereof. The aromatic component may be a feedstream composed by one ormore of the following chemicals like polystyrene, alpha-methyl styrene,vinyl toluene, alkyl substituted indenes and related homologues.

More preferred examples of resins to be used as component (b) are: MBG223, a modified aliphatic hydrocarbon resin, showing a H-NMR aromaticcontent of 11.3%, a Ring and Ball softening point of 88° C.,manufactured by Eastman B. V. and WINGTACK™ 86, a modified hydrocarbonresin, showing a H-NMR aromatic content of 9.6% and a Ring and Ballsoftening point of 86° C., manufactured by GOODYEAR CHEMICALS. Preferredsolid tackifying resins will have Ring and Ball softening points in therange of from 85 to 90° C.

The adhesive composition according to the present invention preferablycomprises from 50 to 300 parts by weight and more preferably from 100 to200 parts by weight of tackifying resin per 100 parts by weight ofcomponent (a).

In preferred adhesive compositions, the component (b) occurs in aproportion of from 35 to 56 wt %, relative to the weight of thecomposition.

Component (c)

Suitable plasticizers include predominantly plasticizing oils that areparaffinic or naphthenic in character (carbon aromatic distribution ≦5%,preferably ≦2%, more preferably 0% as determined according to DIN 51378)and a glass transition temperature lower than −55° C. as measured byDifferential Scanning Calorimetry. Those products are commerciallyavailable from the Royal Dutch/Shell Group of companies, likeSHELLFLEX™, EDELEX™, and ONDINA™ oils. Other oils include KAYDOL™ oilfrom Witco, or TUFFLO™ oils from Arco or NYPLAST™ from NYNAS. Otherplasticizers include compatible liquid tackifying resins like REGALREZ™R-1018 or WINGTACK™ 10.

Other plasticizers may also be added, like olefin oligomers; lowmolecular weight polymers (≦30,000 g/mol) like liquid polybutene, liquidpolylsoprene copolymers, liquid styrene/isoprene copolymers or liquidhydrogenated styrene/conjugated diene copolymers; vegetable oils andtheir derivatives; or paraffin and microcrystalline waxes.

The composition according to the present invention preferably comprisesa plasticizer in a weight proportion of from 5 to 15 wt %, relative tothe weight of the complete composition and of from 10 to 85 parts byweight of plasticizer per 100 parts by weight of block copolymerconstituent (a). Also each block copolymer of component (a) may bepro-blended with a small amount of plasticizer by the manufacturer ofsaid copolymer.

Other Components (Non-Limitative)

Other rubber components may be incorporated into the adhesivecompositions according to the present invention. It is also known in theart that various other components can be added to modify the tack, theodour, the colour of the adhesives. Antioxidants and other stabilizingingredients can also be added to protect the adhesive from degradationinduced by heat, light and processing or during storage.

Several types of antioxidants can be used, either primary antioxidantslike hindered phenols or secondary antioxidants like phosphitederivatives or blends thereof. Examples of commercially availableantioxidants are IRGANOX™ 565 from Ciba-Geigy(2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tertiary-butylanilino)-1,3,5-triazine), IRGANOX 1010 from Ciba-Geigy(tetrakis-ethylene-(3,5-di-tertiary-butyl-4-hydroxy-hydrocinnamate)methane)and POLYGARD™ HR from Uniroyal(tris-(2,4-di-tertiary-butyl-phenyl)phosphite). Other antioxidantsdeveloped to protect the gelling of the polybutadiene segments can alsobe use, like the SUMILIZER™ GS from Sumitomo(2[1-(2-hydroxy-3,5-di-ter-pentylphenyl)ethyl)]4,6-di-tert-pentylphenylacrylate);SUMILIZER T-PD from Sumitomo(pentaerythrythyltetrakis(3-dodecylthiopropionate)); or mixturesthereof.

Preparation of the Composition

No particular limitation is imposed on the preparation process of theadhesive composition. Therefore, there may be used any process such as amechanically mixing process making use of rolls, a Banbury mixer or aDalton kneader, a hot-melt process characterized in that heating andmixing are conducted by using a meting kettle equipped with a stirrer,like a high shear Z-blade mixer or a single- or twin-screw extruder, ora solvent process in which the compounding components are poured in asuitable solvent and stirred, thereby obtaining an intimate solution ofthe pressure sensitive adhesive composition.

Use of the Composition

PSA compositions according to the present invention may be appliedwithout using any solvent (e.g., hot-melt) or in the form of theirsolutions to a base material such as paper or a plastic film by means ofa proper coater, thereby producing various kinds of pressure sensitiveadhesive tapes for tapes or labels which can be used in coldenvironments and which can be used for long storage at low temperatures.

During label manufacture, a laminate of a face stock, pressure sensitiveadhesive layer and a release liner are passed through an apparatus whichconverts the laminate into commercially useful labels and label stock.The process involves, amongst others, die-cutting and matrix strippingto leave labels on a release liner.

It has surprisingly been found that during the manufacture of tapes,labels and bandages according to the present invention, the fouling ofknives used in sitting and cutting of roll and sheet stocks issignificantly reduced.

It will be appreciated that another aspect of the present invention isformed by the use of tapes, labels or bandages on packed frozen articlessuch as food, medicines and the like. A more particular aspect is formedby the use of repositionable or removable tapes or labels on frozenarticles.

The present invention will hereinafter be illustrated more specificallyby the following examples, however without restricting the scope tothese specific embodiments.

Test Methods

Standard peel, tack, cohesion and viscosity tests were carried out onthese formulations as described in the Test method manual for PressureSensitive Tapes from the Pressure Sensitive Tape Council (PSTC), thestandard FINAT test method for Pressure sensitive materials, the AFERAtest methods for Pressure Sensitive Adhesive Tapes and the ASTM relatedmethods. Different testing surfaces have been used in function of theapplication: chromed stainless steel plates (No. 304) (“ss”) asrecommended by the FINAT and Kraft paper.

-   -   Rolling Ball Tack (RBT) is the distance expressed in        centimetres; a steel ball rolls on the adhesive film with a        standard initial velocity (Pressure Sensitive Tape Council Test        No. 6; ASTM 03121-73). Small numbers indicate aggressive tack.    -   Loop Tack (LT) was determined using PSTC5 and FTM 9 loop tack        method. High numbers LT indicate aggressive tack. Results are        expressed in Newton/25 mm (N/25 mm).    -   Peel Adhesion (PA) was determined by Pressure Sensitive Tape        Council Method No. 1 and ASTM D3330-83. Large numbers Indicate        high strength when peeling a test tape from a steel substrate.        Results are expressed in N/25 mm.    -   Holding Power (HP) is the time required to pull a standard area        (2.5×1.3 cm) of tape from a standard test surface (steel=ss)        under a standard load (1 kg, 2 or 5 kg), in shear at 2°        (Pressure Sensitive Tape Council Method No. 7; ASTMD-3654-82).        Long times indicate high adhesive strength. Results are        expressed in hours (h) or minutes (min). The type of failure        mode is expressed as adhesive failure (AF) or cohesive failure        (CF). This test can be carried out at room temperature (about        23° C.) or at a more elevated temperature, depending on the        test.    -   The SHAFT (shear adhesion failure temperature) was measured by        2.5×2.5 cm Mylar to chromed ss plates with a 1 kg weight. The        samples are placed in an oven and the temperature is raised by        22° C./minute. SAFT measures the temperature at which the lap        shear assembly fails.    -   Glass transition temperatures Tg have been determined by        Differential Scanning calorimetry with a temperature sweep of        40° C./min. The Tg is measured at the onset of the transition.    -   Polystyrene content was determined by 1H-NMR.    -   Average homopolymer block lengths have been determined by ¹³C        NMR using the method described herein before. ¹³C NMR spectra of        polymer samples were obtained with a Bruker AMX-500 FT        spectrometer operating at 125 MHz. Quantitative proton-decoupled        spectra were recorded with a 90° ¹³C excitation pulse and a        repetition rate of 10 s. 10% (w/w) of polymer solutions in CDCl₃        were used. To improve the relaxation time 0.1 mol/l chromium        acetylacetonate was added. The applied line broadening was 2 Hz.        The spectra were referenced such that the aliphatic carbons of        trans-polybutadiene are at 31.9 ppm.    -   Quantification of the percentage (%) of aromatic proton in        aromatic modified hydrocarbon resin was done by liquid 1H-NMR        after dissolving the samples in deuterated chloroform and        measuring with a BRUKER DPX-300.    -   Ring and Ball softening point is a measure of the temperature at        which a resin softens following the ASTM E-28 test method.    -   Low temperature conditions: the tack tests have been carried out        in a climate chamber, wherein the temperature could be adjusted        down to 0° C. The RBT has been measured at respectively 23, 15,        10, 5 and 0° C. Prior to testing the samples have been        conditioned at the testing temperature during 24 hours.        Synthesis of the Block Copolymers A and B

Cyclohexane, styrene, butadiene and isoprene were purified by activatedaluminumoxide and stored at 4° C. under a nitrogen atmosphere. EPON 826diglycidyl ether and dibromoethane (EDB) were used as coupling agent.Prior to synthesis, a monomer mixture of butadiene and isoprene (at aweight/weight ratio given in Table 1) was prepared and stored undernitrogen at 4° C. This mixture was used as such.

An autoclave, equipped with a helical stirrer was charged withcyclohexane and the content was heated to 50 to 60° C. As initiatorsec-BuLi was dosed immediately followed by styrene monomer, which wasallowed to polymerize to completion. The reaction temperature wasincreased to 70° C., at which temperature a butadiene/isoprene monomermixture (B/I) was dosed and reacted. The resulting diblock was coupledwith an excess EPON 826 diglycidyl ether or alternatively with an excessof EDB. This excess was optionally scavenged with sec-BuLi and followedby addition of ethanol as terminator. The reaction mixture was cooled to40° C., transported to a blending vessel and a stabilization package wasadded (comprising IRGANOX 565 and tris(nonylphenol)phosphite 0.08/0.35phr as a cyclohexane solution) and stirred at RT. Dry rubber wasobtained by steam coagulation finishing, followed by drying in an oven.

The polymers were analyzed by GPC. Table 1 lists the amounts in whichthe components have been used. The results of the GPC analysis are inTable 2. Further components used in the examples are listed in Table 3.

Synthesis of Polymer with Sequential/Reinitiation (Polymer C)

Cyclohexane, styrene, butadiene and isoprene have been purified byactivated aluminumoxide and were stored at 4° C. under a nitrogenatmosphere.

Prior to synthesis, a monomer mixture of butadiene and isoprene (at thedesired weight/weight ratio) was prepared and stored under nitrogen at4° C. This mixture was used as such. An autoclave, equipped with ahelical stirrer was charged with cyclohexane and the content was heatedto 50° C. As initiator sec-BuLi was dosed immediately followed bystyrene monomer that was allowed to polymerize to completion. Thereaction temperature was increased to 60° C. and followed by dosing andreaction to completion of a butadiene/isoprene monomer mixture (B/I). Asecond portion of sec-BuLi was dosed immediately followed by dosing andreacting to completion of a butadiene/isoprene monomer mixture (B/I). Asecond portion of styrene monomer was dosed and reacted to completion.The reaction mixture was terminated with a stoichiometric amount ofalcohol, cooled to 40° C., transported to a blending vessel and astabilization package was added and stirred at room temperature. Whitepolymer was obtained by steam coagulation finishing, followed by dryingin an oven.

The polymer was analyzed by GPC. The results have been listed in Table2. TABLE 1 Polymer A B C Cyclohexane (l) 77 14 30 Initiator (mmol) 20.527.4 28 Styrene (gram) 300 329 290 B/I (ratio) 1.5 1 1 B/I (gram) 14901637 1230 Initiator (mmol) 23.5 B/I (gram) 2285 EPON 826 (gram) 0.24 EDB(ml) 0.56 Ethanol (ml) 1 1 1

TABLE 2 Polymer A B C Mw Polystyrene *10³ 10.8 10.9 10.9 Total Mw *10³188 245 191 Coupling efficiency % 71 43 68 Polystyrene content wt % 1817 19 B/I ratio 40/60 50/50 50/50 Vinyl in B wt % 8 8 8 Vinyl in I wt %5 5 5

Further components used in the tested adhesive compositions have beenlisted in Table 3. TABLE 3 KRATON D-1160 is a linearstyrene-isoprene-styrene block copolymer with 19% polystyrene content, atotal molecular weight of 178,000 g/mole and a coupling efficiency of100% KRATON D-1113 is a linear styrene-isoprene-styrene block copolymerwith 16% of polystyrene content, a coupling efficiency of 44% and atotal molecular weight of 240,000 g/mole Polymer A is a linearstyrene-isoprene/butadiene-styrene block copolymer with 18% polystyrenecontent, a coupling efficiency of 71%, a weight average total molecularweight of 188,000 g/mole and a isoprene/butadiene w % ratio of 60/40Polymer B is a linear styrene-isoprene/butadiene-styrene block copolymerwith 17% of polystyrene content, a coupling efficiency of 43%, a weightaverage total molecular weight of 245,000 g/mole and anisoprene/butadiene wt % ratio of 50/50 Polymer C is a linearstyrene-(isoprene/butadiene)-styrene block copolymer with a 19 wt %polystyrene content, a weight average total molecular weight of 191 000g/mole and a isoprene/butadiene wt % ratio of 50/50, mixed with astyrene-(isoprene/butadiene) diblock copolymer with a molecular weightof 95,000 g/mole, and a proportion of 30 mol/mole %, relative to thetriblock copolymer KRATON D-1118 is a linear styrene-butadiene-styreneblock copolymer with 31% of polystyrene content, a coupling efficiencyof 22% and a total molecular weight of 170,000 g/mole FINAPRENE 1205 isa styrene-butadiene diblock copolymer with a polystyrene content of 25%,having a total molecular weight of 120,500 g/mole PICCOTAC 1094 is analiphatic hydrocarbon resin with a Ring and Ball softening point of 95°C., a NMR-H aromaticity of 0%, developed by EASTMAN BV MBG 223 is anexperimental aliphatic/aromatic hydrocarbon resin with a Ring and Ballsoftening point of 88° C., a NMR-H aromaticity of 11.3%, a glasstransition temperature Tg of 36° C. developed by EASTMAN BV WINGTACK 86is an aliphatic/aromatic hydrocarbon resin with a Ring and Ballsoftening point of 86° C. and a NMR-H aromaticity of 9.6%, a glasstransition temperature Tg of 37° C. developed by GOODYEAR CHEMICALSQUINTONE S-100 is an aliphatic/aromatic hydrocarbon resin with a Ringand Ball softening point of 94° C. a NMR-H aromaticity of 6.3%, a glasstransition temperature Tg of 49° C. developed by ZEON WINGTACK ET is analiphatic/aromatic hydrocarbon resin with a Ring and Ball softeningpoint of 94° C. a NMR-H aromaticity of 4.2%, a glass transitiontemperature Tg of 44° C. developed by GOODYEAR CHEMICALS PICCOTAC 6085is an aliphatic/aromatic hydrocarbon resin with a Ring and Ballsoftening point of 98° C. a NMR-H aromaticity of 13.5%, a glasstransition temperature Tg of 43° C. developed by EASTMAN ECR 373 is analiphatic/aromatic hydrocarbon resin with a Ring and Ball softeningpoint of 86° C. a NMR-H aromaticity of 11.75%, a glass transitiontemperature Tg of 41° C. developed by EXXON MOBIL Chemicals MBG 222 isan experimental aliphatic/aromatic hydrocarbon resin with a Ring andBall softening point of 85° C. a NMR-H aromaticity of 4%, a glasstransition temperature Tg of 34° C. developed by EASTMAN EDELEX 956 is anaphtenic oil from DEUTSCHE SHELL AG. EDELEX SM 925 is a paraffinic oilfrom DEUTSCHE SHELL AG IRGANOX is an anti-oxidant from CIBA

All the formulations in the examples have been prepared out of solvent.The different ingredients were poured in toluene and mixed for 24 hoursto obtain the dissolution. Afterward, the solutions have been coated ona Polyester Film (Mylar −36 microns thick) with an automatic Bar Coaterto obtain an adhesive coating weight of 22 g/m² dry. Thereafter, thesamples have been laminated with a siliconised paper to protect them.Prior to testing, the samples are stored in a conditioned room at 21° C.and 50% relative humidity.

EXAMPLE 1

The adhesive properties of formulations based on a SIS and the polymer Aand C (described in Table 1) are compared in Table 4. Particularly, theRolling Ball Tack has been measured at different temperatures, as low as+5° C. in this case.

It is clearly demonstrated that the combination of polymer A and theWINGTACK 86 allows to have good tack properties at low temperature, muchbetter than SIS in the same formulation. TABLE 4 F-1 Ingredients unitsComp F-2 F-3 KRATON D-1160 phr 100 Polymer A phr 100 Polymer C phr 100WINGTACK 86 phr 110 110 110 EDELEX 956 N phr 10 10 10 IRGANOX 1010 phr 33 3 RTB at +23° C. cm 12 1.6 4 RTB at +15° C. cm >40 3.4 9.5 RTB at +10°C. cm — 4 25 RTB at +5° C. cm — 23 Loop Tack 23° C. N/25 mm 15 15 16Peel Adhesion 23° C. N/25 mm 18 12 13 Holding Power 2 kg/23° C.hours >100 50 >100

EXAMPLE 2

The adhesive properties of formulations based on SIS and polymer B(described in Table 1) are presented in Table 5.

The glass transition temperatures are calculated with the help of theFox Equation (Handbook of Pressure Sensitive Adhesive Technology—DonSatas—1989—page 369). The Rolling Ball Tack has been measured atdifferent decreasing temperatures down to 0° C.

At the same ingredient ratio and same formulation composition(Formulations F-4 and Formulation F-6), the polymer B allows to achievebetter tack at lower temperature than the SIS formulation. If thecomposition of the SIS formulation (F-4) is adjusted to have the sameformulation glass transition temperature Tg of −25° C. as that of theF-6 containing the polymer B, then the Formulation F-5 is obtained thatcontains a higher level of oil, namely 85 phr versus of 40.

This higher amount of oil in Formulation F-5 improved the Rolling BallTack values but has the following detrimental effects:

the other adhesive properties tack, peel adhesion, cohesion and SAFT(Shear Adhesive Failure temperature) are much lower and therefore theadhesive properties are not well balanced;

the higher oil content will enhance the oil bleeding in the frontmaterial, like paper in labels, creating undesirable side effects (oilyspots that reduces the aesthetics of the paper surface) and modificationof the adhesive properties;

the higher oil content is also the responsible for the edge oozing ofthe adhesive because of the lower cohesion, and provokes the mutualsticking of adjacent tape rolls and that of stacked sheets.

Therefore, the polymers of the invention are well designed to developadhesives with lower service temperature than SIS but with the markedadvantage to use less oil or plasticizer. TABLE 5 units CompF-4 CompF-5F-6 D-1113 phr 100 100 Polymer B phr 100 WINGTACK 86 phr 140 140 140EDELEX 956 phr 40 85 40 IRGANOX 1010 phr 3 3 3 calculated Tg ° C. −18−25 −25 RBT at +23° C. cm 2 1.2 1 RBT at +15° C. cm 3.5 1.7 2 RBT at+10° C. cm >40 2.3 3.5 RBT at +5° C. cm 6.3 19.5 RBT at 0° C. cm >30 >30LT N/25 mm 17 12 15 PA N/25 mm 15 8 14 HP ss 1 kg min 660 216 1560 HP ss2 kg min 240 48 190 SAFT ° C. 80 75 85

EXAMPLE 3

In label adhesives, SIS polymers are often blended with SB or SBS blockcopolymers to make the formulation softer and better suited for thelabel converting, namely the die-cutting and matrix stripping processes(U.S. Pat. No. 5,663,228 (AVERY DENNISON) 02.09.1997). However, itshould be noticed that blends of polymers of the present invention, likePolymer A, B and C with SIS, SBS and SB are miscible and give only onetan delta peak as measured by Dynamic mechanical analysis.

Table 6 shows the Pressure Sensitive Adhesive results obtained forSIS/SB and Polymer B/SB and SBS. Results from Formulations F-7/F-8 showthat an aliphatic resin is not good for a Polymer B/SB blend (F-8) asthere is no tack measured neither by the Rolling ball Tack nor by theLoop Tack.

The combination of Polymer B/SB with MBG 223 (F-9) and WINGTACK 86(F-10) provide to the formulations good tack properties at lowertemperature than SIS. It is also seen in Formulation F-11 compoundedthat with a paraffinic oil, having a lower glass transition temperatureTg than the naphtenic oil, that the Rolling ball tack values areexcellent even at temperature as low as 0° C.

Properties obtained with blends of Polymer B/SB (F-11) and Polymer B/SRS(F-12) are similar with slightly better cohesion with the formulationF-12 because SBS is a triblock copolymer. It should also be pointed outthat the adhesive of Formulation F-11 has the characteristics of being agood removable adhesive. Applied on a paper surface, this adhesive canbe easily removed even after a prolonged storage period. TABLE 6 F12Ingredients Units F-7 F-8 F-9 F-10 F-11 comp D-1113 phr 44 Polymer B phr44 44 44 44 44 SOLPRENE 1205 phr 56 56 56 56 56 KRATON phr 56 D-1118PICCOTAC 1094 phr 100 100 MBG 223 phr 100 WINGTACK 86 phr 100 100 100EDELEX 956 phr 63 63 63 63 EDELEX 925 phr 63 63 IRGANOX 1010 phr 3 3 3 33 3 RBT at +23° C. cm 5 >40 2 1.6 1.5 1.7 RBT at +15° C. cm 21 3 2 2.2 2RBT at +10° C. cm >40 8 1.7 2 2.3 RBT at +5° C. cm 8 2 2.1 2.3 RBT at 0°C. cm n.m >30 7 9 Loop tack N/25 mm 16 0 15 11 7 6 Peel Adhesion N/25 mm13 16 15 13 5.6 6 HP 2 kg hours 0.3 0.4 0.5 12 6 18n.m = not measured

EXAMPLE 4

The rolling Ball Tack values in function of the temperature for severaladhesive formulations based on different hydrocarbon resins are shown inTable 7. The formulations tested were polymer/hydrocarbonresin/oil/anti-oxidant in a ratio 100/110/15/3, based on parts perhundred of rubber (phr). Formulation F-17 and F-18 have better lowtemperature RBT values because both WINGTACK 86 and MBG223 have theappropriate balance of glass transition temperature Tg, NMR-Haromaticity and R&B Softening points.

In the Table, the following abbreviations are used:

QUINTONE S100; WINGTACK ET; PICCOTAC 6095; ECR 373; WINGTACK 86; MBG223; MBG 222. TABLE 7 Ingredients Units F-13 F-14 F-15 F-16 F-17 F-18F19 Type of S100 ET 6095 373 86 223 222 resin Tg resin ° C. 49 44 43 4137 36 34 Aromatic % 6.3 4.2 13.5 11.8 9.6 11.3 4 H-NMR Aromatic % 19 1340 36 28 32 12 R & B ° C. 94 94 98 89 86 88 85 soft. Point RBT at cm 1716 17 10 3.9 8.3 14 +23° C. RBT at cm >30 >30 >30 >30 3.8 16 >30 +15° C.RBT at cm 7 >30 +10° C. RBT at cm >30 +5° C.

EXAMPLE 5

Table 8 shows the influence of the butadiene-isoprene weight % ratio onthe RBT values at different temperatures. The formulations tested werepolymer/WINGTACK 86/oil/antioxidant in a ratio 100/110/15/3 based onparts per hundred of rubber. Polymer D is similar to polymer C describedin Table 3 but has a butadiene-isoprene weight % ratio of 70-30. PolymerE is similar to polymer C but with a butadiene-isoprene weight % ratioof 30-70. Results indicate the improvement in tack as the butadienecontent increases. TABLE 8 I/B RBT at RBT at RBT at RBT at For- % wt 23°C. 15° C. 10° C. 5° C. mulation Ingredients ratio (cm) (cm) (cm) (cm)F-20 Polymer D 30/70 2.1 2.6 5.9 9.4 F-21 Polymer C 50/50 1.6 4 3.4 23F-22 Polymer E 70/30 2.1 5.4 18 >>30 F-23 D-1160 100/0  12 >>30 CompTechnical Field

An adhesive composition comprising

1. one or more styrenic block copolymers,

2. one or more tackifier resins, and

3. one or more plasticizers.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. An adhesivecomposition for tapes, labels and bandages to be used at temperatures of+5° C. and lower, said adhesive composition comprising (a) at least oneblock copolymer, comprising at least two terminal blocks of poly(vinylaromatic compound) and at least one midblock of a randomly copolymerizedmixture of isoprene and butadiene, wherein the weight ratio betweenisoprene and butadiene is in the range of from 70:30 to 30:70,optionally mixed with a diblock copolymer comprising one poly(vinylaromatic compound) block and one randomly copolymerized mixture ofisoprene and butadiene, and optionally mixed with a block copolymer,comprising at least one block of poly(vinyl aromatic compound) and atleast one block of poly(butadiene) or poly(isoprene), (b) at least onemixed aliphatic/aromatic tackifying resin or a blend of aliphatic andaromatic tackifying resins, having an aromatic H-NMR content between 6and 22%, wherein the tackifying resin has a glass transition temperatureTg between 30° C. and 40° C., and a Ring an Ball softening point between80° C. and 90° C., and (c) a plasticizer in an amount of at most 25 wt%, relative to the weight of the adhesive composition.
 11. The adhesivecomposition of claim 10, wherein said component (a) mainly consists of aS-(I/B)-S or [S-(I/B)]_(n)X block copolymer, optionally mixed with adiblock copolymer S(I/B), and optionally mixed with minor amounts of oneor more block copolymers, selected from the group of S-B, S-B-S, S-I andS-I-S, wherein S represents a poly(vinyl aromatic compound) block, (I/B)represents a block of a randomly polymerized mixture of isoprene andbutadiene, wherein the weight ratio between isoprene and butadiene is inthe range of from 70:30 to 30:70, and wherein B represents apoly(butadiene) block, wherein I represents an poly(isoprene) block. 12.The adhesive composition of claim 11 wherein the contents of S-B, S-I,S-B-S and/or S-I-S block copolymers is in the range of from 0 to 50 wt%, relative to the weight of the component (a).
 13. The adhesivecomposition of claim 10 wherein component (b) has an aromatic H-NMRcontent between 9 and 22%.
 14. The adhesive composition of claim 13wherein component (b) has an aromatic H-NMR content between 9 and 18%.15. The adhesive composition of claim 10 wherein component (b) occurs ina proportion of from 35 to 55 wt %, relative to the weight of thecomposition.
 16. The adhesive composition of claim 14 wherein component(b) occurs in a proportion of from 35 to 55 wt %, relative to the weightof the composition.
 17. The adhesive composition of claim 10 wherein theS blocks in the block copolymers of component (a) are poly(styrene)blocks and wherein the proportion of bound styrene in the main S-(I/B)-Sor [S-(I/B)]_(n) X block copolymers is in the range of from 10 to 40 wt%.
 18. The adhesive composition of claim 16 wherein the S blocks in theblock copolymers of component (a) are poly(styrene) blocks and whereinthe proportion of bound styrene in the main S-(I/B)-S or [S-(I/B)]_(n) Xblock copolymers is in the range of from 10 to 40 wt %.
 19. Tape, labelsand bandages, comprising a substrate layer and an adhesive compositionapplied thereon, said adhesive composition comprising (a) at least oneblock copolymer, comprising at least two terminal blocks of poly(vinylaromatic compound) and at least one midblock of a randomly copolymerizedmixture of isoprene and butadiene, wherein the weight ratio betweenisoprene and butadiene is in the range of from 70:30 to 30:70,optionally mixed with a diblock copolymer comprising one poly(vinylaromatic compound) block and one randomly copolymerized mixture ofisoprene and butadiene, and optionally mixed with a block copolymer,comprising at least one block of poly(vinyl aromatic compound) and atleast one block of poly(butadiene) or poly(isoprene), (b) at least onemixed aliphatic/aromatic tackifying resin or a blend of aliphatic andaromatic tackifying resins, having an aromatic H-NMR content between 6and 22%, wherein the tackifying resin has a glass transition temperatureTg between 30° C. and 40° C., and a Ring an Ball softening point between80° C. and 90° C., and (c) a plasticizer in an amount of at most 25 wt%, relative to the weight of the adhesive composition.
 20. Tapes, labelsand bandages comprising a substrate layer and an adhesive compositionapplied thereon, wherein said tapes labels and bandages are used attemperatures of +5° C. or lower and said adhesive composition comprises:(a) at least one block copolymer, comprising at least two terminalblocks of poly(vinyl aromatic compound) and at least one midblock of arandomly copolymerized mixture of isoprene and butadiene, wherein theweight ratio between isoprene and butadiene is in the range of from70:30 to 30:70, optionally mixed with a diblock copolymer comprising onepoly(vinyl aromatic compound) block and one randomly copolymerizedmixture of isoprene and butadiene, and optionally mixed with a blockcopolymer, comprising at least one block of poly(vinyl aromaticcompound) and at least one block of poly(butadiene) or poly(isoprene),(b) at least one mixed aliphatic/aromatic tackifying resin or a blend ofaliphatic and aromatic tackifying resins, having an aromatic H-NMRcontent between 6 and 22%, wherein the tackifying resin has a glasstransition temperature Tg between 30° C. and 40° C., and a Ring an Ballsoftening point between 80° C. and 90° C., and (c) a plasticizer in anamount of at most 25 wt %, relative to the weight of the adhesivecomposition.